The author's application of psychoanalysis to these problems has the directness and explicitness which we are accustomed to find in Freud's own writings. This is as true in the literary portion of the work as in the medical but it never intrudes to mar the intrinsic beauty of certain of the selections nor the force of the intuitive revelations which the writers of the preceding science have made in regard to sleep walking and walking in the moonlight. Sadger has skilfully utilized these revelations to convince us of the truth of the psychoanalytic discoveries and has used the latter only to make still more explicitly and scientifically clear the testimony of the poetic writers and to point out the applicability of their material to medical problems. The choice of this little understood and little studied subject and its skilful presentation on the part of the author, as well as the introduction to the reader of the literary productions of which use has been made, give the book a peculiar interest and value. It is also of especial service in its brief but profoundly suggestive study of the psychic background of Shakespeare's creative work as illustrated in the sleep walking of Lady Macbeth. The endeavor in the translation has been to make accessible to our English readers the clear and direct psychoanalysis of the author and the peculiar psychologic and literary value of the book. INTRODUCTION[1] [1] Über Nachtwandeln und Mondsucht. Eine medizinisch-literarische Studie, von Dr. J. Sadger, Nervenarzt in Wien; Schriften zur angewandten Seelenkunde, Herausgegeben von Prof. Dr. Sigm. Freud, Sechzehntes Heft, Leipzig und Wien, Franz Deuticke, 1914. Sleep walking or night wandering, known also by its Latin name of noctambulism, is a well-known phenomenon. Somnambulism is not so good a term for it, since that signifies too many things. In sleep walking a person rises from his bed in the night, apparently asleep, walks around with closed or half opened eyes, but without perceiving anything, yet performs all sorts of apparently purposeful and often quite complicated actions and gives correct answers to questions, without afterward the least knowledge of what he has said or done. If this all happens at the very time and under the influence of the full moon, it is spoken of as moon walking or being moonstruck. Under the influence of this heavenly body the moonstruck individual is actually enticed from his bed, often gazes fixedly at the moon, stands at the window or climbs out of it, "with the surefootedness of the sleep walker," climbs up upon the roof and walks about there or, without stumbling, goes into the open. In short, he carries out all sorts of complex actions. Only it would be dangerous to call the wanderer by name, for then he would not only waken where he was, but he would collapse frequently and fall headlong with fright if he found himself on a height.